Gentex Corp

Gentex passes most Buffett tests, but the margin of safety depends on base-case assumptions.

Gentex makes electrochromic automatic-dimming rearview mirrors and sells them to carmakers, and since April 2025 it has also owned VOXX, a consumer audio and aftermarket electronics business. Revenue reached $2.5B in the latest year, and return on equity has averaged 19% across fifteen years of filings with no loss years. Owner earnings have grown slowly, at 2.0% a year, and the company carries almost no debt. At a share price of $21.01, the base-case value is $33.96, but the bear case of $20.01 sits just below the price, and the price-to-earnings ratio is 12×.

Gentex makes electrochromic automatic-dimming rearview mirrors. These mirrors darken by themselves to cut headlight glare, and the company sells them to carmakers and their suppliers. The company says it is the leading maker of these mirrors and the largest supplier to the automotive industry. Most automotive sales run on annual purchase orders that set prices for each vehicle model but not quantities, so revenue follows the production of the models that carry its parts. Since April 2025 the company has also owned VOXX, which adds consumer audio and aftermarket electronics, a business the filing describes as price sensitive.

• Light vehicle production volumes in North America, Europe and Asia
• Option rates for mirrors with electronic features such as the Full Display Mirror
• Annual customer price reductions, offset only in part by cost cuts
• Tariffs and counter-tariffs on exports, especially into China
• Consumer audio and aftermarket sales from the VOXX acquisition

Inside the circle? A careful owner can estimate the core mirror business with reasonable confidence, since the filings show no loss years and a return on equity averaging 19%. The estimate weakens because the business sells into a cyclical car industry, faces annual price cuts, and changed shape with the 2025 VOXX acquisition, which leaves little time to test the combined company. Camera-based rear vision is a technology risk that the company itself flags, and its operating margin has moved around its average by 4.2%.

A moat is an advantage that stops rivals from taking a business's profits, and Gentex's clearest one looks like switching costs: carmakers buy its mirrors under annual purchase orders and some long-term agreements, though the excerpts do not say what changing supplier would cost. Its patents and trademarks add a second layer, although the filing says no single patent is necessary for its products. Returns agree that something protects profits, with return on equity averaging 19% and return on invested capital averaging 23%, and no loss years. Operating margin has slipped from an average of 24% to 19%, and the company reports ongoing pricing pressure, so pricing power looks weak. I would call the moat narrow: it protects a core mirror business that is still exposed to camera substitution, Chinese rivals and tariffs, and the excerpts do not show how long it will last.

Gentex spends its cash on plant and equipment, research, acquisitions and share buybacks. In 2025 much of the new spending went into acquisitions, led by the VOXX purchase, and the excerpts do not show what those businesses earn on the cash paid. The share count has fallen steadily, which helps owners, but the retained earnings test (-0.5×) fails, so the cash kept in the business has not yet created matching market value. The dividend is small, with an average payout of 29%, and total debt is only $3.8M. The filing is frank about tariffs, pricing pressure and competition, but its language on VOXX leans on belief about future growth, so treat those claims as management's view until the results show it.

• The diluted share count has changed by -3.2% a year over the period, so buybacks have reduced the number of shares owners hold a claim on.
• Retained earnings of $2.5B have not, on the engine's test, created matching market value (-0.5×). A Buffett-style owner would ask whether that cash could have been returned or used at higher returns.
• Return on equity fell to 16% in the latest year, against a long-run average of 19%, while the shares trade at 1.8× book value.
• The excerpts give no return target, payback period or post-deal results for the VOXX purchase, so this part of capital allocation cannot be checked from the filing.

• FailsThe $1 retained testFails

  Each dollar retained over the period has been matched by -0.5× of market value created ($2.5B retained in total).

  Why this test
• PassesDemonstrated, consistent earning powerPasses

  No loss years across 15 years of filings, with operating margin varying by 4.2% around its average.

  Why this test

Several of Buffett's documented tests pass. The engine finds consistent earning power, high return on equity, low debt and owner earnings all pass, and the owner-earnings yield of 8.9% sits above the 10-year Treasury yield of 5.1%, which matches his point that interest rates act like gravity on values. The retained earnings test fails at -0.5×. Buffett asks whether each dollar kept in a business creates at least a dollar of value for owners, and so far the cash kept has not done that. On pricing power, the filing says: 'Historically, annual customer price reductions have placed pressure on gross margin on an annual basis.' That is the reverse of the pricing power Buffett treats as the most important test, so the moat looks narrow. Switching costs are its clearest source, but the excerpts do not show what a carmaker would pay to change supplier. The engine verdict is within margin. The base case clears the margin of safety, but the bear case falls below the price, so the protection depends on which case you believe.

• Core Gentex sales and auto-dimming mirror shipments in the next annual report

  The filing says core sales fell in 2025 and mirror shipments dropped, so the trend in the core business is the main test of the moat.

• Gross margin against the range the company gives for calendar year 2026

  The company says it hopes to offset annual customer price reductions, so whether it does is the direct test of pricing power.

• VOXX sales, operating income and any goodwill impairment

  The company bought VOXX in April 2025 and has not yet shown what it earns on the cash paid for it.

• Share repurchases compared with owner earnings and the business's intrinsic value

  Buybacks only make sense below intrinsic value, and the retained earnings test is failing, so the repurchase record needs checking against value.

• Camera-based rear vision gaining share in more markets

  The filing names changes in preferences 'such as cameras replacing mirrors and/or autonomous driving' as a source of increased competition.

Questions the filings couldn't answer

• What do VOXX and the other 2025 acquisitions earn on the cash paid for them? The excerpts do not give that return.
• What would it cost a carmaker to switch supplier? The excerpts do not say, so the strength of the switching-cost moat is unproven.
• Will the retained earnings test improve as the new businesses mature, or will the cash kept in the business keep failing to create value?